Electric vehicles, hybrid electric vehicles (HEV's), and indeed any vehicle that utilizes an electric machine, such as an electric motor, may be configured to use the electric machine to provide regenerative braking to at least assist in stopping the vehicle. In addition, non-electric vehicles may also be configured to provide regenerative braking, for example, through the use of a hydraulic system. Regenerative braking provides a number of advantages over using a friction braking system exclusively. For example, the use of regenerative braking, whereby an electric motor provides negative torque to the vehicle wheels, reduces wear on the friction elements of the friction braking system. In addition, during regenerative braking, the motor can function as a generator, producing electricity that can be used immediately, or stored in a storage device, such as a battery.
Because of the advantages associated with regenerative braking, some regenerative braking control systems may attempt to apply the maximum regenerative braking torque so that overall vehicle efficiencies are maximized. It may be desirable to avoid this strategy, however, when the vehicle, and thus the motor, is operating at a very low speed. This is because although the motor is capable of producing very high torque at low speeds, it does so with poor efficiency. Therefore, the regenerative braking torque may be controlled to gradually reduce to zero at low vehicle speeds. Although this strategy may provide efficiencies, under certain conditions the vehicle operator may experience an inconsistent braking feel when the friction brakes engage. This may be true, for example, if the regenerative braking is ramped out quickly and the friction brakes takeover in a very short period of time. This may be especially true when the friction brakes are cold.